GSM-SIM800L | Code | Circuit | Pin configuration


SIM800L GSM/GPRS module is a miniature GSM module, You can use this module to design a simple Mobile to perform SMS text messages, make or receive phone calls, connecting to the internet through GPRS and TCP/IP. Sim800L module supports quad-band GSM/GPRS network, it works pretty much anywhere in the world and it supports the Micro SIM card.

Model number: SIM800L

Other names: GSM modem, GSM module

Other related devices: SIM900A, SIM800A, A6 GPRS GSM Module



  • SIM800L is small in size and it supports Micro SIM card
  • Sim800L module supports quad-band GSM/GPRS network

Pin Configuration

Pin Name  

Pin Description


 Helical Antenna interface


Power supply(3.4v - 4.4v)


Hard RESET pin, pull this pin low for 100ms to perform a hard reset.


Serial Communication – Data Receiving pin


Serial Communication – Data Transmitting pin


GND connection


Differential Speaker Positive Terminal


Differential Speaker Negative Terminal


Differential microphone Negative pin 


Differential microphone Positive pin


 Pin activates/deactivates sleep mode. Pulling it HIGH will put the module in sleep mode, disabling serial communication. Pulling it LOW will wake the module up


The pin acts as a Ring Indicator. It is basically the ‘interrupt’ out pin from the module. It is by default high and will pulse low for 120ms when a call is received. It can also be configured to pulse when an SMS is received.

Technical Specifications

Power supply: 3.3v to 4.4v
Current Required: 1A – 2.5 A
Baud rate: 9600 bps
Sim: Micro sim
Temparature Range: -40 ̊ C to +80 ̊̊ C
Data GPRS: GPRS Data Downlink Transfer: max 85.6 kbps
GPRS Data Uplink Transfer: max 85.6 kbps
SMS storage: SIM card
Real Time clock: Support RTC
Firmware upgrade: Serial port or USB port

How to use SIM800L

GSM-Sim800L can  be tested by using  “AT” commands, 

insert the micro-SIM card as shown below

GSM SIM800L,GSM,SIM800L,TechnoElectronics44

GSM-SIM800L signal Light indication

1. Initially the signal light will blink continuously every second there is no network connection.

2. After a certain time when it receives the signal the light blinks every 3 seconds means GSM is ready for calls and messages.
3. Otherwise we request data mode, so signal-light will blink every 2 seconds.

every 1-second
GSM-SIM800L without network signal-LED blinks every one second

every 3-second
GSM-SIM800L with network signal-LED blinks every three second

USB-TTL(CP210X) interface with GSM   

1. Install driver software CP210X, communication between GSM and computer



2. Find the comport number on the computer

Ex: my computer->devicemanager->ports->com6)


Check the COMPORT number

3. Connect the GSM module with the computer by using a USB-TTL converter

4. Install the Flash-Magic Tool 

5. Open the Flash-Magic Tool and set the com port, baud rate. 
And enter the “AT” commands

FlashMagic Tool -TechnoElectronics44
FlashMagic Tool

FlashMagic Tool-TechnoElectronics
FlashMagic Tool

SIM800L testing Using “AT” commands

AT: Ok
ATD: Dail a call
ATH: Hang up the call
AT+CMGF=1 (set the sim800L in text message mode)
AT+CMGR=2(Read the message at second place)
AT+CMGD=1,4 (Delete all messages)
AT+CMGD= N(enter a number  'N'  to delete message number)
Ex: AT+CMGD=2 (Delete the second message in the Simcard)
AT+CMGS=+ZZxxxxxxxxxx(Enter mobile number-message sending to the phone number)
AT+CNMI=2,1,0,0,0 (New SMS Message Indications)
AT+CMGL="ALL"(Read the specified type of all messages)

FlashMagic-GSM -TechnoElectronics44


GSM SIM800L interface with Arduino

  • GSM SIM800L TX – Arduino 8(Rx)
  • GSM SIM800L RX – Arduino 9(Tx)
  • GSM SIM800L GND – Atrduino GND

Circuit diagram

Arduino Code for GSM-SIM800L    



1.Communicate with long-distance
2. IOT Embedded firmware design
3. Load control using GSM
4. GSM-based mobile phone design

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